Ana Barrio

Impaired Mesopic Visual Acuity in Eyes with Early Age-Related Macular Degeneration

PURPOSE To determine photopic and mesopic distance high-contrast visual acuity (HC-VA) and low-contrast visual acuity (LC-VA) in eyes with early age-related macular degeneration (AMD). METHODS Measurements were made in 22 subjects with early AMD and 28 healthy control subjects. Inclusion criteria included a photopic HC-VA of 20/25 or better. Distance VA was measured using HC (96%) and LC (10%) Bailey-Lovie logMAR letter charts under photopic (85 cd/m(2)) and mesopic (0.1-0.2 cd/m(2)) luminance conditions. RESULTS Mean mesopic distance HC-VA and LC-VA were significantly worse (0.1 logMAR and 0.28 logMAR, respectively) in the early AMD group than in the control group. Under mesopic conditions, the mean difference between LC-VA and HC-VA was significantly greater in the early AMD (0.45 logMAR) than the control group (0.27 logMAR). Mean differences between mesopic versus photopic HC-VA and mesopic versus photopic LC-VA were significantly greater in the early AMD than the control group (0.13 and 0.32 logMAR of difference between the means, respectively). Sensitivity and specificity were significantly greater for mesopic LC-VA than for mesopic HC-VA (Receiver Operating Characteristics, area under the curve [AUC], 0.94 ± 0.030 and 0.76 ± 0.067, respectively). AUC values for photopic HC-VA and LC-VA were below 0.70. CONCLUSIONS Visual acuity testing under low luminance conditions emerged as an optimal quantitative measure of retinal function in early AMD.

Normal Values for the Size of a Halo Produced by a Glare Source

PURPOSE To determine the size of a halo in the visual field induced by bright light in healthy eyes of all ages using the Vision Monitor (MonCv3; Metrovision, Pérenchies, France) and to assess the repeatability of the method. METHODS Measurements were made in the right eyes of 147 healthy subjects (mean age: 48.2 ± 16.2 years) who were classified into six age groups. Using the Vision Monitor, optotypes of low luminance were presented at a distance of 2.5 m. The visual angle subtended by the radius of the halo was calculated in minutes of arc (arc min). The repeatability of the method was determined in a subset of 37 subjects older than 50 years by calculating the Bland-Altman coefficient of repeatability. RESULTS The mean radius of the halo was 111.6 ± 39.8 arc min. Halo radius started to increase significantly from the age of 50 to 59 years. The relationship between halo radius and age (r = 0.65; P < .0001) was described by fitting a power function to the data. Halo size was independent of gender. The coefficient of repeatability of the method was ±44 arc min. CONCLUSIONS Halo size increases with age following a power model. The normal halo size values provided could help clinicians distinguish between normal or abnormal glare problems. The intersession repeatability observed for halo size measurement indicates this method could be useful for assessing visual impairment caused by glare.

Comparing methods of determining addition in presbyopes

Background:  The use of plus lenses to compensate for the reduction in the range of accommodation associated with presbyopia, brings the near point of accommodation to a comfortable distance for near visual tasks. Our aim was to compare the tentative near addition determined using the most common procedures with the final addition prescribed in presbyopic patients.

The Computer-Vision Symptom Scale (CVSS17): development and initial validation.

PURPOSE To develop a questionnaire (in Spanish) to measure computer-related visual and ocular symptoms (CRVOS). METHODS A pilot questionnaire was created by consulting the literature, clinicians, and video display terminal (VDT) workers. The replies of 636 subjects completing the questionnaire were assessed using the Rasch model and conventional statistics to generate a new scale, designated the Computer-Vision Symptom Scale (CVSS17). Validity and reliability were determined by Rasch fit statistics, principal components analysis (PCA), person separation, differential item functioning (DIF), and item-person targeting. To assess construct validity, the CVSS17 was correlated with a Rasch-based visual discomfort scale (VDS) in 163 VDT workers, this group completed the CVSS17 twice in order to assess test-retest reliability (two-way single-measure intraclass correlation coefficient [ICC] and their 95% confidence intervals, and the coefficient of repeatability [COR]). RESULTS The CVSS17 contains 17 items exploring 15 different symptoms. These items showed good reliability and internal consistency (mean square infit and outfit 0.88-1.17, eigenvalue for the first residual PCA component 1.37, person separation 2.85, and no DIF). Pearsons correlation with VDS scores was 0.60 (P < 0.001). Intraclass correlation coefficient for test-retest reliability was 0.849 (95% confidence interval [CI], 0.800-0.887), and COR was 8.14. CONCLUSIONS The Rasch-based linear-scale CVSS17 emerged as a useful tool to quantify CRVOS in computer workers. : Spanish Abstract.

Effect of driver distraction and low alcohol concentrations on useful field of view and frequency-doubling technology perimetry

Purpose:  To investigate the effects of a mental psychometric task that simulates the distraction effect of a hands‐free mobile phone and of low alcohol concentrations (0.3–0.5 g/l) on two tests: the useful field of view (UFOV) and frequency‐doubling technology (FDT) perimetry.

Relationship between macular pigment and visual acuity in eyes with early age-related macular degeneration.

Purpose:  Today the extent to which MP impacts visual function in early AMD remains unclear. This study examines the relationship between macular pigment optical density (MPOD) and high‐contrast visual acuity (HC‐VA) and low‐contrast visual acuity (LC‐VA) in eyes with early age‐related macular degeneration (AMD).

Intraexaminer repeatability and agreement in stereoacuity measurements made in young adults

AIM To determine the repeatability and agreement of stereoacuity measurements made using some of the most widely used clinical tests: Frisby, TNO, Randot and Titmus. METHODS Stereoacuity was measured in two different sessions separated by a time interval of at least 24h but no longer than 1wk in 74 subjects of mean age 20.6y using the four methods. The study participants were divided into two groups: subjects with normal binocular vision and subjects with abnormal binocular vision. RESULTS Best repeatability was shown by the Frisby and Titmus [coefficient of repeatability (COR): ±13 and ±12s arc respectively] in the subjects with normal binocular vision though a clear ceiling effect was noted. In the subjects with abnormal binocular vision, best repeatability was shown by the Frisby (COR: ±69s arc) and Randot (COR: ±72s arc). In both groups, the TNO test showed poorest agreement with the other tests. CONCLUSION The repeatability of stereoacuity measures was low in subjects with poor binocular vision yet fairly good in subjects with normal binocular vision with the exception of the TNO test. The reduced agreement detected between the tests indicates they cannot be used interchangeably.

Repeatability of the Modified Thorington Card Used to Measure Far Heterophoria

Purpose To determine the interexaminer and intraexaminer repeatability of the modified Thorington test (TH) for distance vision in young adults and to compare these results with those observed for the heterophoria tests most commonly used in clinical practice. Agreement among tests was also assessed. Methods Distance heterophoria was quantified on two separate occasions by two examiners in 110 subjects aged 18 to 32 years (mean, 19.74 years; SD, 2.5 years) using four different tests: cover test (CT) Von Graefe, Maddox rod, and modified TH. The repeatability of the tests and agreement between them was estimated by the Bland and Altman method whereby the mean difference and the 95% limits of agreement were determined as the coefficient of repeatability (COR) and coefficient of agreement. Results The Thorington test showed best interexaminer repeatability (COR = ±1.43&Dgr;), followed closely by CT (COR = ±1.65&Dgr;), whereas best intraexaminer repeatability was observed for CT (COR = ±1.28&Dgr;) followed by TH (COR = ±1.51&Dgr;). Among the different combinations of tests, TH and CT showed best agreement indicated by the lowest coefficient of agreement (±2.23&Dgr;) and a low mean difference (−0.63&Dgr;) between measurements. Conclusions Good interexaminer and intraexaminer repeatability was observed for both TH and CT, and agreement between the two tests was also good. Given the simple administration of the TH, we recommend its clinical use to quantify distance horizontal heterophoria.

Relationship between halo size and forward light scatter

Purpose To determine the relationship between the size of a halo induced by a glare source and forward scatter or visual acuity (VA) in healthy eyes. Method Measurements were made in the right eyes of 51 healthy individuals of mean age 29.3±7.5 years. Halo radius was measured using the Vision Monitor and low luminance (1 cd/m2) optotypes presented at a distance of 2.5 m. The visual angle subtended by the radius of the halo was calculated in minutes of arc (arc min). Forward scatter or, straylight, was measured using the compensation comparison technique. Best-corrected distance VA was measured using high contrast (HC) (96%) and low contrast (LC) (10%) Bailey-Lovie logMAR letter charts under photopic (85 cd/m2) and mesopic (0.15 cd/m2) luminance conditions. Results Mean halo radius was 202±43 arc min (3.4±0.7°) and mean retinal straylight was 0.95±0.12 log units. Mean photopic distance HC-VA and LC-VA were −0.02±0.06 and 0.12±0.09 logMAR, respectively. Mean mesopic distance HC-VA and LC-VA were 0.35±0.11 and 0.74±0.11 logMAR, respectively. Forward stepwise regression analysis revealed that halo radius was significantly correlated with straylight (r=0.45) and mesopic LC-VA (r=0.48), but not with photopic HC-VA and/or LC-VA and mesopic HC-VA. Conclusions In healthy eyes, the larger the halo size induced by a given glare source, the greater the forward-scatter (straylight) and worse the mesopic LC-VA. Halo size seems to be independent of photopic HC-VA or LC-VA and mesopic HC-VA.

The validity and repeatability of the New Aniseikonia Test.

Purpose. Aniseikonia has been traditionally measured using the New Aniseikonia Test (NAT) based on red/green anaglyphs. This study was designed to establish whether the NAT is a valid and reliable test. Methods. The NAT was tested on three groups of subjects: a control group (n = 45) and two groups of participants at risk of experiencing aniseikonia, those with anisometropia greater than or equal to 1.00 D (n = 29) and those with bilateral pseudophakia (n = 26). The validity of the test was established by comparing the measured aniseikonia with that simulated with size lenses in a double-blind study. Repeatability was evaluated by comparing the results obtained at two different time points. Results. Our results indicate that the NAT underestimates aniseikonia and more so in the horizontal than in the vertical direction. Repeatability was poor, although biases were clinically insignificant. However, the 95% limits of agreement were around ±2%. The behavior of the test was similar in the three groups of subjects. Conclusions. We conclude that the repeatability of the NAT is not very high and recommend that clinicians be cautious when interpreting the results of this test.